title: Why a large tip electrode makes a deeper radiofrequency lesion: effects of increase in electrode cooling and electrode-tissue interface area.
abstract: BACKGROUND
  Increasing electrode size allows an increase in radiofrequency lesion depth. The purpose of this study was to examine the roles of added electrode cooling and electrode-tissue interface area in producing deeper lesions.
  
  
  RESULTS
  In 10 dogs, the thigh muscle was exposed and superfused with heparinized blood. An 8-French catheter with 4- or 8-mm tip electrode was positioned against the muscle with a blood flow of 350 mL/min directed around the electrode. Radiofrequency current was delivered using four methods: (1) electrode perpendicular to the muscle, using variable voltage to maintain the electrode-tissue interface temperature at 60 degrees C; (2) same except the surrounding blood was stationary; (3) perpendicular electrode position, maintaining tissue temperature (3.5-mm depth) at 90 degrees C; and (4) electrode parallel to the muscle, maintaining tissue temperature at 90 degrees C. Electrode-tissue interface temperature, tissue temperature (3.5- and 7.0-mm depths), and lesion size were compared between the 4- and 8-mm electrodes in each method. In Methods 1 and 2, the tissue temperatures and lesion depth were greater with the 8-mm electrode. These differences were smaller without blood flow, suggesting the improved convective cooling of the larger electrode resulted in greater power delivered to the tissue at the same electrode-tissue interface temperature. In Method 3 (same tissue current density), the electrode-tissue interface temperature was significantly lower with the 8-mm electrode. With parallel orientation and same tissue temperature at 3.5-mm depth (Method 4), the tissue temperature at 7.0-mm depth and lesion depth were greater with the 8-mm electrode, suggesting increased conductive heating due to larger volume of resistive heating because of the larger electrode-tissue interface area.
  
  
  CONCLUSIONS
  With a larger electrode, both increased cooling and increased electrode-tissue interface area increase volume of resistive heating and lesion depth.
authors.affiliation: Department of Medicine, University of Oklahoma Health Sciences Center, Department of Veterans Affairs Medical Center, Oklahoma City 73104, USA.
authors.forename: K
authors.initials: K
authors.lastname: Otomo
authors.forename: W S
authors.initials: WS
authors.lastname: Yamanashi
authors.forename: C
authors.initials: C
authors.lastname: Tondo
authors.forename: M
authors.initials: M
authors.lastname: Antz
authors.forename: J
authors.initials: J
authors.lastname: Bussey
authors.forename: J V
authors.initials: JV
authors.lastname: Pitha
authors.forename: M
authors.initials: M
authors.lastname: Arruda
authors.forename: H
authors.initials: H
authors.lastname: Nakagawa
authors.forename: F H
authors.initials: FH
authors.lastname: Wittkampf
authors.forename: R
authors.initials: R
authors.lastname: Lazzara
authors.forename: W M
authors.initials: WM
authors.lastname: Jackman
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000295:instrumentation* / Q000379:methods; D004285:Dogs; D004566:Electrodes; D018482:Muscle, Skeletal / Q000601:surgery; D011846:Radio Waves; D013696:Temperature; D013848:Thigh / Q000601:surgery